In recent years, there has been an increased focus on reducing emissions of greenhouse gases generated by burning fossil fuels. One solution for reducing greenhouse gas emissions is developing renewable sources of energy. Particularly, energy derived from the wind has proven to be an environmentally safe and reliable source of energy, which can reduce dependence on fossil fuels.
Energy in wind can be captured by a wind turbine, which is a rotating machine that converts the kinetic energy of the wind into mechanical energy, and the mechanical energy subsequently into electrical power. Common horizontal-axis wind turbines include a tower, a nacelle located at the apex of the tower, and a rotor that is supported in the nacelle by means of a shaft. The shaft couples the rotor either directly or indirectly with a rotor assembly of a generator housed inside the nacelle. A plurality of wind turbines may be arranged together to form a wind park or wind power plant.
Wind power plants are coupled to an electrical network or grid which distributes electrical power by means of circuit breakers. As wind power plants are generally situated in rural areas, infrastructure is generally inadequately set up to support the wind power plant electrical distribution. As a result, such electrical grids which are far from the main generation units experience a phenomena known as “weak grid”.
In large wind power plants connected to a weak grid, large fault current contributions are required to maintain system stability. However, the present assignees of the application have discovered that during conditions when the grid short circuit strength increases, the fault current contribution could exceed the breaking capacity of the circuit breaker. This issue is exacerbated in situations when additional power production units, for example more wind turbines, or gas turbines or coal plants, are added onto the transmission circuit of a wind power plant, and in situations of a fault, append their fault contribution onto the transmission circuit of the wind power plant. This leads to further stress on the circuit breaker, which may permanently damage when undertaking a disconnection by opening a circuit which has been loaded with current that exceeds its rating.
The present invention seeks to provide a solution to address the above situation.